1. Field of the Invention
This invention relates to a power transmission chain, and more particularly to a power transmission chain and a power transmission apparatus suited for a continuously variable transmission (CVT) of a vehicle such as an automobile.
2. Related Art
As a continuously variable transmission for an automobile, there is know the type (as shown in FIG. 4) which comprises a driving pulley 2 having a fixed sheave 2a and a movable sheave 2b and operatively connected to an engine, a driven pulley 3 having a fixed sheave 3b and a movable sheave 3a and operatively connected to a drive wheel, and an endless power transmission chain 1 extending around the two pulleys. Each movable sheave 2b, 3a is moved toward and away from the corresponding fixed sheave 2a, 3b by a hydraulic actuator, and by doing so, the chain 1 is clamped by hydraulic pressure, and by this clamping force, a contact load is caused to develop between each pulley 2, 3 and the chain 1, and a torque is transmitted by a frictional force of this contact portion.
As the power transmission chain 1, there is known the type (as shown in FIG. 5) which comprises a plurality of links 30 having front and rear passage portions (through holes) 31 and 32 for the passage of pins 34A, 34B, 35A and 35B therethrough, and the plurality of first pins 34A and 34B and the plurality of second pins 35A and 35B which interconnect the links 30 arranged in a width of the chain in such a manner that the front passage portion 31 of one link 30 corresponds to the rear passage portion 32 of other link 30 so that the links 30 can be bent relative to each other in a direction of a length of the chain. The first pin 34A, 34B fixedly fitted in the front passage portion 31 of one link 30 and movably fitted in the rear passage portion 32 of other link 30 and the mating second pin 35A, 35B movably fitted in the front passage portion 31 of the one link 30 and fixedly fitted in the rear passage portion 32 of the other link 30 move relative to each other in rolling contact with each other so that the links 30 can be bent relative to each other in the chain lengthwise direction (See JP-A-2006-002783 Publication).
In JP-A-2006-002783 Publication, it is proposed to use two kinds of combinations of pins 34A, 34B, 35A and 35B having the rolling contact surfaces of different shapes. Namely, in FIG. 5, the rolling contact surface of one first pin 34A is formed into an involute surface with a base radius (a radius of a base circle) R1, and the rolling contact surface of the other first pin 34B is formed into an involute surface with a base radius R2, and by doing so, noises are reduced.
With respect to the two kinds of pins having the rolling contact surfaces of different shapes, the difference in the base radius is such that for example, one is 100 while the other is 130, and the profiles or contours of the two rolling contact surfaces are almost the same when viewed with the eyes, and the two kinds of actual products (pins) can not be discriminated from each other, and there has been a possibility that wrong pins are inadvertently mixed in the pins.